TECHNICAL FIELD
[0001] The present invention relates to the use of a refrigerating oil composition for the
natural substance-based refrigerants ammonia, propane, butane and carbon dioxide.
BACKGROUND ART
[0002] In general, refrigerators such as compression type refrigerators comprising a compressor,
a condenser, an expansion valve and an evaporator have a structure in which a mixed
fluid of a refrigerant and a lubricating oil is circulated in the closed system. Heretofore,
chlorofluorocarbons such as dichlorodifluoromethane (R-12) and chlorodifluoromethane
(R-22) have been used as the refrigerant for the compression-type refrigerators and
various types of lubricating oils have been produced and used in combination with
the refrigerant. However, since there is the anxiety that the chlorofluorocarbons
cause environmental pollution such as ozonosphere destruction in stratosphere when
these substances are released into the atmosphere, the regulation on the chlorofluoro
carbons is becoming stricter worldwide. Due to this situation, novel refrigerants
such as hydrofluorocarbons and fluorocarbons, typical examples of which include 1,1,1,2-tetrafluoroethane
(R-134a), are attracting attention. Although there is no anxiety that the hydrofluorocarbons
and the fluorocarbons destruct the ozonosphere, there is the fear that these substances
might cause global warming due to the longevity of these substances in the atmosphere.
Therefore, the use of natural substance-based refrigerants that do not cause the above
problems is considered.
[0003] Among the natural substance-based refrigerants, ammonia has heretofore been used
for industrial refrigerators that require oil agents and refrigerants in great amounts.
As the refrigerating oil for such refrigerators, mineral oils have been used. However,
since mineral oils and ammonia are not miscible with each other, additional apparatuses
such as an apparatus for separation of the oil are indispensable. Therefore, the system
becomes great and, moreover, the performance of the system is not sufficiently satisfactory.
[0004] In
JP 05 0094 83 A, it is disclosed that polyalkylene glycols which do not have hydroxyl group at any
of the ends have excellent miscibility with ammonia and contribute to improvement
in the performance to a great extent. It is described in the specification of the
above application that additives conventionally used for refrigerating oils such as
extreme pressure agents and antioxidants can be used. However, the use of the additives
is not shown in the examples.
[0005] In
JP 06 010081 A , additives advantageously used in combination with ammonia or hydrofluorocarbon
refrigerants are disclosed. However, the use of the additives specifically described
in the examples is limited to the use in combination with hydrofluorocarbon refrigerants.
[0006] Lubricating oil compositions for a specific use, namely for hydrogen-containing fluorohydrocarbon
refrigerants, are described in
US A 5,368,765.
[0007] The document EP
US A 5,595,678 describes lubricants for ammonia. These lubricants are a polyalkylene glycol with
a molecular weight of 200 to 4000, which may be blended with further components such
as a mineral oil. The polyalkylene glycol compound according to the document is end-capped
with either an aromatic group or an alkyl group, in the last case the number of carbon
atoms is a minimum of ten.
[0008] The use of polyalkylene glycols in refrigeration systems with ammonia is described
in
US A 5,413,728. Further components such as mineral oils may be present, but obviously only in residual
amounts due to previous use, a residual amount may be thought to be below 1% by weight
of the overall composition.
[0009] The document
DE 44 04 804 A1 teaches the use of polyalkylene glycols in refrigeration systems with ammonia. Mineral
oils as further components are not mentioned.
[0010] Lubricating oil compositions for refrigerant systems on the basis of a Freon gas
are described in
JP 58 103594 A.
[0011] The document
EP A 0 989 180 is a document under Article 54(3) EPC. This document describes lubricating oils to
be used in refrigerating machines using ammonia as the refrigerant. The oil comprises
a polypropylene glycol monoether and may furthermore comprise a different type of
oil.
[0013] In general, since ammonia has a greater reactivity than other refrigerants and exhibits
basic property by itself, acidic substances have been considered to be unsuitable
for use in combination with ammonia. On the other hand, most of the additives are
actually acidic substances. This situation causes insufficient lubrication and the
improvement has been desired. The present situation described above is reflected on
the fact that the above references have no specific descriptions on the use of combinations
of ammonia with conventional additives. It has not been found whether the combinations
can be used for practical applications.
[0014] The present invention has an object of providing a refrigerating oil composition
having excellent miscibility with natural substance-based refrigerants and, in particular,
with ammonia-based refrigerants and exhibiting an improved lubricity.
[0015] As the result of extensive studies by the present inventors, it was found that the
object of the present invention could be effectively achieved when the refrigerating
oil composition comprises a synthetic oil component comprising a polyether compound
having a specific property and a mineral oil component comprising sulfur in specific
relative amounts, and the amount of the sulfur components is in the range of 5 to
1,000 ppm in the composition. The present invention has been completed based on this
finding.
DISCLOSURE OF THE INVENTION
[0016] The use of the refrigerating oil composition for natural substance-based refrigerants
of the present invention has the following aspects:
- (1) Use of a refrigerating oil composition which comprises
- (A) a synthetic oil component comprising a polyether compound having a pour point
of -10°C or lower and
- (B) a mineral oil component comprising sulfur components, the mineral oil component
having a pour point of -5°C or lower and a content of sulfur of 0.01 to 5.00% by weight,
wherein (A):(B) which is the ratio of the amount by weight of the component (A) to
the amount by weight of the component (B) is in the range of 25:75 to 99:1 and the
content of sulfur derived from component (B) in the composition is in the range of
5 to 1,000 ppm,
wherein said polyether compound is a polyalkylene glycol compound represented by general
formula (1):
R1-O-A-R2 (1)
wherein R1 and R2 each represent hydrogen atom or an alkyl group having 1 to 4 carbon atoms, one of
R1 and R2 represents an alkyl group having 1 to 4 carbon atoms and the other of R1 and R2 represents hydrogen atom; A represents a chain of a homopolymer of propylene oxide
or a copolymer of ethylene oxide and propylene oxide; and, when the number of the
ethylene oxide units is represented by m and the number of the propylene oxide units
is represented by n, m and n satisfy the following relations: 0 ≤ m/n ≤ 10 and 5 ≤
m+n ≤ 100,
for refrigerating systems using a natural substance-based refrigerant selected from
the group consisting of ammonia, propane, butane and carbon dioxide.
- (2) Use of a refrigerating oil composition which comprises
- (A) a synthetic oil component comprising a polyether compound having a pour point
of -10°C or lower and
- (B) a mineral oil component comprising sulfur components, the mineral oil component
having a pour point of -5°C or lower and a content of sulfur of 0.01 to 5.00% by weight,
wherein (A):(B) which is the ratio of the amount by weight of the component (A) to
the amount by weight of the component (B) is in the range of 25:75 to 99:1 and the
content of sulfur derived from component (B) in the composition is in the range of
5 to 1,000 ppm, and
wherein the polyether compound is a polyvinyl ether compound,
for refrigerating systems using a natural substance-based refrigerant selected from
the group consisting of ammonia, propane, butane and carbon dioxide.
- (3) Use described in (1) or (2), wherein said natural substance-based refrigerant
comprises 90% by weight or more of ammonia.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017]
Figure 1 shows a flow diagram that exhibits an example of the compression type refrigerating
cycle of the "compressor - condenser - expansion valve-evaporator" system having an
oil separator and a hot gas line.
Figure 2 shows a flow diagram that exhibits an example of the compression type refrigerating
cycle of the "compressor - condenser - expansion valve-evaporator" system having an
oil separator.
Figure 3 shows a flow diagram that exhibits an example of the compression type refrigerating
cycle of the "compressor - condenser - expansion valve-evaporator" system having a
hot gas line.
Figure 4 shows a flow diagram which exhibits an example of the compression type refrigerating
cycle of the "compressor - condenser - expansion valve-evaporator" system.
[0018] Descriptions of the numerical symbols in the Figures are as the followings:
- 1:
- A compressor
- 2:
- A condenser
- 3:
- An expansion valve
- 4:
- An evaporator
- 5:
- An oil separator
- 6:
- A hot gas line
- 7:
- A valve for a hot gas line
THE MOST PREFERRED EMBODIMENT TO CARRY OUT THE INVENTION
[0019] It is necessary that the polyether compound used in the present invention have a
pour point of -10°C or lower. It is preferable that the kinematic viscosity at 100°C
is 3 to 50 mm
2/s. It is more preferable that the kinematic viscosity is 3 to 45 mm
2/s and the pour point is -15°C or lower. When the kinematic viscosity is lower than
3 mm
2/s, the lubricity is not sufficiently exhibited at high temperatures. When the kinematic
viscosity exceeds 50 mm
2/s, miscibility with ammonia markedly decreases and power loss increases. Therefore,
the anxiety that an efficient operation cannot be completed increases. When the pour
point is higher than -10°C, resistance to flow at low temperature increases and efficiency
and the lubricities are adversely affected.
[0020] The polyether compound used in the present invention is not particularly specified
as long as the above requirements are satisfied. Polyalkylene glycol compounds and
polyvinyl ether compounds are suitable as the polyether compound. Polyalkylene glycol
compounds represented by the foregoing general formula (1) are more suitable as the
polyalkylene glycol compound.
[0021] In the foregoing general formula (1) representing the polyalkylene glycol compound,
R
1 and R
2 each represent hydrogen atom or an alkyl group having 1 to 4 carbon atoms such as
methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl
group, isobutyl group and tert-butyl group, one of R
1 and R
2 represents an alkyl group having 1 to 4 carbon atoms and the other of R
1 and R
2 represents hydrogen atom. The compound may have various copolymer structures such
as structures of a block copolymer, a random copolymer and an alternating copolymer.
m and n represent numbers satisfying the following relations: 0 ≦m/n≦ 10, preferably
0≦m/n≦3 and more preferably 0≦m/n≦2; and 5 ≦m+n≦ 100 and preferably 5≦m+n≦50.
[0022] In the present invention, apart from the polyalkylene glycol compound represented
by the foregoing general formula (1), a polyalkylene glycol compound of an ethylene
oxide-propylene oxide copolymer represented by the following general formula (2):

can also be used as the polyether compounds. In the general formula (2), R
3, R
4 and R
5 each represent hydrogen atom or an alkyl group having 1 to 4 carbon atoms, at least
one of R
3, R
4 and R
5 represents an alkyl group having 1 to 4 carbon atoms and A is the same as defined
above for general formula (1).
[0023] Examples of the alkyl group having 1 to 4 carbon atoms represented by R
3, R
4 or R
5 in the general formula (2) include methyl group, ethyl group, n-propyl group, isopropyl
group, n-butyl group, sec-butyl group, isobutyl group and tert-butyl group. At least
one of R
3, R
4 and R
5 represents an alkyl group having 1 to 4 carbon atoms. When the value represented
by m/n exceeds 10 in general formula (1) or (2) representing the compound used for
the refrigerating oil composition of the present invention, a drawback arises in that
the compound becomes waxy and the miscibility becomes poor. When the value represented
by m+n is smaller than 5, a drawback arise in that the viscosity is excessively small
and the lubricity becomes poor. When the value represented by m+n exceeds 100, a drawback
arises in that the miscibility and the efficiency of heat exchange become poor due
to a high viscosity.
[0024] Examples of the polyvinyl ether compound include polyvinyl ether compounds comprising
constituting units represented by general formula (3):

wherein R
5, R
6 and R
7 each represent hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, the
atom and the groups represented by R
5, R
6 and R
7 may be the same with or different from each other, R
8 represents a divalent hydrocarbon group having 1 to 10 carbon atoms, R
9 represents a hydrocarbon group having 1 to 20 carbon atoms, k represent numbers giving
an average value of 0 to 10, the atom and the groups represented by R
5 to R
9 may be the same or different among different constituting units and, when a plurality
of R
8O are present, the plurality of R
8O may represent the same group or different groups.
[0025] Polyvinyl ether compounds comprising block or random copolymers comprising the constituting
units represented by the foregoing general formula (3) and constituting units represented
by the following general formula (4):

can also be used as the polyether compounds. In the general formula (4), R
10 to R
13 each represent hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms and
the atom and the groups represented by R
10 to R
13 may be the same with or different from each other and may be the same or different
among different constituting units.
[0026] In the foregoing general formula (3), R
5, R
6 and R
7 each represent hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms and
preferably 1 to 4 carbon atoms. The atom and the groups represented by R
5, R
6 and R
7 may be the same with or different from each other. Examples of the hydrocarbon group
include alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl
group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, various types
of pentyl groups, various types of hexyl groups, various types of heptyl groups and
various types of octyl groups; cycloalkyl groups such as cyclopentyl group, cyclohexyl
group, various types of methylcyclohexyl groups, various types of ethylcyclohexyl
groups and various types of dimethylcyclohexyl groups; aryl groups such as phenyl
group, various types of methylphenyl groups, various types of ethylphenyl groups and
various types of dimethylphenyl groups; and arylalkyl groups such as benzyl group,
various types of phenylethyl groups and various types of methylbenzyl groups. It is
preferable that R
5, R
6 and R
7 represent hydrogen atom.
[0027] On the other hand, R
8 in general formula (3) represents a divalent hydrocarbon group having 1 to 10 carbon
atoms and preferably 2 to 10 carbon atoms. Examples of the divalent hydrocarbon group
having 1 to 10 carbon atoms include divalent aliphatic groups such as methylene group,
ethylene group, phenylethylene group, 1,2-propylene group, 2-phenyl-1,2-propylene
group, 1,3-propylene group, various types of butylene groups, various types of pentylene
groups, various types of hexylene groups, heptylene groups, various types of octylene
groups, various types of nonylene groups and various types of decylene groups; alicyclic
groups having two bonding portions on an alicyclic hydrocarbon such as cyclohexane,
methyl-cyclohexane, ethylcyclohexane, dimethylcyclohexane and propylcyclo-hexane;
divalent aromatic hydrocarbon groups such as various types of phenylene groups, various
types of methylphenylene groups, various ethylphenylene groups, various types of dimethylphenylene
groups and various types of naphthylene groups; alkylaromatic groups having one monovalent
bonding portion on each of the alkyl portion and the aromatic portion of alkylaromatic
hydrocarbons such as toluene, xylene and ethylbenzene; and alkylaromatic hydrocarbon
groups having bonding portions on alkyl group portions of polyalkylaromatic hydrocarbons
such as xylene and diethylbenzene. Among the above groups, aliphatic groups having
2 to 4 carbon atoms are preferable.
[0028] Further, k in general formula (3) represent numbers showing the repeating numbers
of the group represented by R
8O and giving an average value in the range of 0 to 10 and preferably in the range
of 0 to 5. When a plurality of R
8O are present, the plurality of R
8O may represent the same group or different groups.
[0029] Furthermore, R
9 in general formula (3) represents a hydrocarbon group having 1 to 20 carbon atoms
and preferably 1 to 10 carbon atoms. Examples of the hydrocarbon group represented
by R
9 include alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl
group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, various types
of pentyl groups, various types of hexyl groups, various types of heptyl groups, various
types of octyl groups, various types of nonyl groups and various types of decyl groups;
cycloalkyl groups such as cyclopentyl group, cyclohexyl group, various types of methylcyclohexyl
groups, various types of ethylcyclohexyl groups, various types of propylcyclohexyl
groups and various types of dimethylcyclohexyl groups; aryl groups such as phenyl
group, various types of methylphenyl groups, various types of ethylphenyl groups,
various types of dimethylphenyl groups, various types of propylphenyl groups, various
types of trimethylphenyl groups, various types of butylphenyl groups and various types
of naphthyl groups; and arylalkyl groups such as benzyl group, various types of phenylethyl
groups, various types of methylbenzyl groups, various types of phenylpropyl groups
and various types of phenylbutyl groups. The atom and the groups represented by R
5 to R
9 may be the same or different among different constituting units.
[0030] It is preferable that polyvinyl ether compound (i) comprising the constituting units
represented by the foregoing general formula (3) has a ratio of the number by mole
of carbon to the number by mole of oxygen in the range of 4.2 to 7.0. When this ratio
is smaller than 4.2, the compound is hygroscopic to a great extent. When the ratio
exceeds 7.0, miscibility with the refrigerant occasionally becomes poor.
[0031] In the foregoing general formula (4), R
10 to R
13 each represent hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms and
the atom and the groups represented by R
10 to R
13 may be the same with or different from each other. Examples of the hydrocarbon group
having 1 to 20 carbon atoms include the groups described above as the examples of
the hydrocarbon group represented by R
9 in the foregoing general formula (3). The atom and the groups represented by R
10 to R
13 may be the same or different among different constituting units.
[0032] It is preferable that polyvinyl ether compound (ii) comprising a block or random
copolymer comprising the constituting units represented by general formula (3) and
the constituting units represented by general formula (4) has a ratio of the number
by mole of carbon to the number by mole of oxygen in the range of 4.2 to 7.0. When
this ratio is smaller than 4.2, the compound is hygroscopic to a great extent. When
the ratio exceeds 7.0, miscibility with the refrigerant occasionally becomes poor.
[0033] In the present invention, a mixture of the polyvinyl ether compound (i) and the polyvinyl
ether compound (ii) may also be used. Polyvinyl ether compounds (i) and (ii) used
in the present invention can be produced by polymerization of the corresponding vinyl
ether monomer and copolymerization of the corresponding hydrocarbon monomer having
an olefinic double bond and the corresponding vinyl ether monomer, respectively.
[0034] As the polyvinyl ether compound used in the present invention, polyvinyl ether compounds
having the following end structures are preferable:
[0035] Polyvinyl ether compounds that have one end having the structure represented by general
formula (5) or (6):

wherein R
14, R
15 and R
16 each represent hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, the
atoms and the groups represented by R
14, R
15 and R
16 may be the same with or different from each other, R
19, R
20, R
21 and R
22 each represent hydrogen atom or a hydrocarbon group having 1 to 20 carbon atom, the
atoms and the groups represented by R
19, R
20, R
21 and R
22 may be the same with or different from each other, R
17 represents a divalent hydrocarbon group having 1 to 10 carbon atoms, R
18 represents a hydrocarbon group having
l to 20 carbon atoms,
p represent numbers giving an average value of 0 to 10 and, when a plurality of R
17O are present, the plurality of R
17O may represent the same group or different groups, and the other end having the structure
represented by general formula (7) or (8):

wherein R
23, R
24 and R
25 each represent hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, the
atoms and the groups represented by R
23, R
24 and R
25 may be the same with or different from each other, R
28, R
29, R
30 and R
31 each represent hydrogen atom or a hydrocarbon group having 1 to 20 carbon atom, the
atoms and the groups represented by R
28, R
29, R
30 and R
31 may be the same with or different from each other, R
26 represents a divalent hydrocarbon group having 1 to 10 carbon atoms, R
27 represents a hydrocarbon group having 1 to 20 carbon atoms,
q represent numbers giving an average value of 0 to 10 and, when a plurality of R
26O are present, the plurality of R
26O may represent the same group or different groups; and
[0036] Polyvinyl ether compounds which have one end having the structure represented by
the foregoing general formula (5) or (6) and the other end having the structure represented
by general formula (9):

wherein R
32, R
33 and R
34 each represent hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms and
the atoms and the groups represented by R
32, R
33 and R
34 may be the same with or different from each other.
[0037] Among the above polyvinyl ether compounds, the following compounds are preferably
used in the present invention:
- (a) Compounds which have one end having the structure represented by general formula
(5) or (6) and the other end having the structure represented by general formula (7)
or (8) and comprise the structural units represented by general formula (3) in which
R5, R6 and R7 each represent hydrogen atoms, k represent numbers of 0 to 4, R8 represents a divalent hydrocarbon group having 2 to 4 carbon atoms and R9 represents a hydrocarbon group having 1 to 20 carbon atoms;
- (b) Compounds which comprise the structural units represented by general formula (3)
alone and have one end having the structure represented by general formula (5) and
the other end having the structure represented by general formula (7), wherein R5, R6 and R7 in general formula (3) each represent hydrogen atom, k represent numbers of 0 to 4, R8 represents a divalent hydrocarbon group having 2 to 4 carbon atoms and R9 represents a hydrocarbon group having 1 to 20 carbon atoms;
- (c) Compounds which have one end having the structure represented by general formula
(5) or (6) and the other end having the structure represented by general formula (9)
and comprise the structural units represented by general formula (3) in which R5, R6 and R7 each represent hydrogen atom, k represent numbers of 0 to 4, R8 represents a divalent hydrocarbon group having 2 to 4 carbon atoms and R9 represents a hydrocarbon group having 1 to 20 carbon atoms; and
- (d) Compounds which comprise the structural units represented by general formula (3)
alone and have one end having the structure represented by general formula (5) and
the other end having the structure represented by general formula (8), wherein R5, R6 and R7 in general formula (3) each represent hydrogen atom, k represent numbers of 0 to 4, R8 represents a divalent hydrocarbon group having 2 to 4 carbon atoms and R9 represents a hydrocarbon group having l to 20 carbon atoms.
[0038] In the present invention, polyvinyl ether compounds which comprise the structural
unit represented by the foregoing general formula (3) and have one end having the
structure represented by the foregoing general formula (5) and the other end having
the structure represented by the following general formula (10):

can also be used. In general formula (10) R
35, R
36 and R
37 each represent hydrogen atom or a hydrocarbon group having
l to 8 carbon atoms and the atoms and the groups represented by R
35, R
36 and R
37 may be the same with or different from each other; R
38 and R
40 each represent a divalent hydrocarbon group having 2 to 10 carbon atoms and may represent
the same group or different groups; R
39 and R
41 each represent a hydrocarbon group having 1 to 10 carbon atoms and may represent
the same group or different groups;
c and
d each represent numbers giving an average value of 0 to 10 and may represent the same
number or different numbers; when a plurality of R
38O are present, the plurality of R
38O may represent the same group or different groups; and, when a plurality of R
40O are present, the plurality of R
40O represent the same group or different groups.
[0039] Further, examples of the polyvinyl ether compounds which can be used in the present
invention include homopolymers or copolymers of alkyl vinyl ethers comprising structural
units represented by general formula (11) or (12):

wherein R
42 represents a hydrocarbon group having 1 to 8 carbon atoms, and having a weight-average
molecular weight of 300 to 5,000 and one end having the structure represented by general
formula (13) or (14):
-CH=CHOR
44 (14)
wherein R
43 represents an alkyl group having 1 to 3 carbon atoms and R
44 represents a hydrocarbon group having 1 to 8 carbon atoms.
[0041] The mineral oil component used in the present invention is not particularly specified.
Examples of the mineral oil component include distilled oils obtained by atmospheric
distillation of paraffinic crude oils, intermediate crude oils and naphthenic crude
oils, distilled oils obtained by vacuum distillation of residual oils of the atmospheric
distillation and purified oils obtained by purifying the above oils in accordance
with a conventional process such as oils purified with solvents, oils purified by
hydrogenation, oils treated by dewaxing and oils treated with white clay. The mineral
oil component has a pour point of -5°C or lower and a content of sulfur of 0.01 to
5.00% by weight. When the pour point is higher than -5°C, the pour point of the refrigerating
oil composition obtained by mixing with the polyether compound is elevated and there
is the possibility that fluidity becomes poor. When the content of sulfur is outside
the above range, there is the anxiety that the effect of addition is not exhibited
or stability deteriorates to cause formation of sludge.
[0042] It is necessary that (A):(B), the ratio of the amount by weight of component (A)
comprising the polyether compound to the amount by weight of component (B) comprising
the sulfur component, is in the range of 25:75 to 99:1. When the ratio is less than
the aforementioned range, the sufficient properties cannot be exhibited due to decreases
in fluidity at low temperatures and miscibility with ammonia. When the ratio exceeds
the aforementioned range, the effect of addition of the mineral oil component cannot
be expected. It is preferable that the ratio is in the range of from 25:75 to 75:25.
[0043] It is necessary that the refrigerating oil composition of the present invention comprises
sulfur components derived from the mineral component in an amount of 5 to 1,000 ppm
and preferably 50 to 500 ppm. Therefore, the amount of the used mineral oil component
is adjusted in accordance with the content of the sulfur components in the mineral
oil component so that the content of sulfur in the refrigerating oil composition is
adjusted in the above range. When the content of the sulfur components in the refrigerating
oil composition is less than 5 ppm, the expected effect of the addition to provide
the lubricity is not exhibited. When the content of the sulfur components exceeds
1,000 ppm, the stability deteriorates and the fear of formation of sludge increases.
To the refrigerating oil composition for natural substance-based refrigerants of the
present invention, where necessary, extreme pressure agents, acid catchers, antioxidants
and anticorrosion agents are added.
[0044] In the present invention, the natural substance-based refrigerant means ammonia,
propane, butane, and carbon dioxide. The lubricating oil composition of the present
invention is effective, in particular, for ammonia-based refrigerants, i.e., refrigerating
systems containing 90% by weight or more of ammonia. The lubricating oil composition
of the present invention is also effective for other natural substance-based refrigerating
systems. In the process for lubricating refrigerators using the refrigerating oil
composition of the present invention, it is preferable that the ratio of the amount
by weight of the above natural substance-based refrigerant to the amount by weight
of the above refrigerating oil composition is in the range of 99/1 to 10/90. When
the amount of the refrigerant is less than the above range, the refrigerating ability
becomes poor. When the amount of the refrigerant exceeds the above range, the lubricity
deteriorates. Therefore, amounts outside the above range are not preferable. From
the above standpoint, it is more preferable that the ratio of the amount by weight
of the refrigerant to the amount by weight of the refrigerating oil composition is
in the range of 95/5 to 30/70.
[0045] The refrigerating oil composition of the present invention can be applied to various
types of refrigerators. In particular, the refrigerating oil composition of the present
invention is advantageously applied to compression-type refrigerating cycles in industrial
compression-type refrigerators in which the oil agents and the refrigerant are required
in great amounts. For example, the refrigerating oil composition can be advantageously
applied to refrigerators disclosed in EP 0 485 979 A, JP 08 259 975 A,
JP 08 240 362A,
JP08 253 779A,
JP08 240 352 A,
EP 0 496 937 A,
JP 08 226 717A and
JP08 231 972A. For example, the advantageous effects can be exhibited when the refrigerating oil
composition of the present invention is applied to compression-type refrigerating
cycles having an oil separator and/or a hot gas line such as the refrigerating cycles
shown in Figures 1 to 3.
EXAMPLE
[0046] The present invention will be described below in further details with reference to
the following examples.
[0047] The test methods used in the examples were as follows.
[Stability]
[0048] Into an autoclave having an inner volume of 20 ml, 7 g of a sample oil, 3 g of a
refrigerant of ammonia gas and a metal catalyst containing copper, aluminum and iron
were placed and water was added to the system in an amount such that the content of
water was adjusted to 1,000 ppm. After the autoclave was closed and kept at 150°C
for 14 days, the sample oil was analyzed.
[Load of seizure]
[0049] The load of seizure was measured in accordance with the method of ASTM D-3233 with
a rotation speed of 290 rpm at the room temperature.
[Examples 1 to 4 and Comparative Examples 1 to 6]
[0050] The test of stability and the measurement of the load of seizure were conducted using
the refrigerating oil compositions shown in Table 1. The results are shown in Table
2.
Components (A) and (B) are abbreviated as follows in Table 1.
Component (A) (The synthetic oil component)
PAG-1:Polyoxypropylene glycol dimethyl ether
PAG-2: Polyoxyethylene(10)oxypropylene(90) glycol mono(n-butyl) ether
PAG-3: Polyoxyethylene(20)oxypropylene(80) glycol monoethyl ether
PVE-1: A copolymer of polyethyl vinyl ether (90) and polyisobutyl vinyl ether (10)
PVE-2: A copolymer of polyethyl vinyl ether (70) and polyisobutyl vinyl ether (30)
Component (B) (The mineral oil component)
The kinematic viscosity at 40°C: 11.6 mm
2/s
The kinematic viscosity at 100°C: 2.84 mm
2/s
The content of sulfur: 0.06%
The pour point: -45°C
Table 1
|
Component (A) |
Component (B) |
Composition |
type |
kinematic viscosity at 100°C (mm2/S) |
pour point (°C) |
composition |
composition |
kinematic viscosity at 40°C (mm2/s) |
content of sulfur (ppm) |
Comparative Example 1 |
PAG-1 |
17.8 |
-50> |
74 |
26 |
49.5 |
153 |
Example 1 |
PAG-2 |
20.8 |
-50> |
58 |
42 |
38.3 |
255 |
Example 2 |
PAG-3 |
25.1 |
-50> |
46 |
54 |
31.4 |
322 |
Example 3 |
PVE-1 |
12.5 |
-50> |
36 |
64 |
22.4 |
395 |
Example 4 |
PVE-2 |
11.4 |
-50> |
53 |
47 |
32.4 |
283 |
Comparative Example 2 |
PAG-1 |
17.8 |
-50> |
100 |
0 |
99.4 |
5> |
Comparative Example 3 |
PAG-2 |
20.8 |
-50> |
100 |
0 |
129.8 |
5> |
Comparative Example 4 |
PAG-3 |
25.1 |
-50> |
100 |
0 |
160.0 |
5> |
Comparative Example 5 |
PVE-1 |
12.5 |
-50> |
100 |
0 |
130.0 |
5> |
Comparative Example 6 |
PVE-2 |
11.4 |
-50> |
100 |
0 |
113.3 |
5> |
composition: the ratio of the amount by weight of Component (A) to the amount by weight
of Component (B) |
Table 2
|
Stability |
Load of seizure |
appearance of oil |
precipitates |
metal catalyst |
total acid value after test (mgKOH/g) |
(N) |
Comparative Example 1 |
good |
none |
no change |
0.01 |
3560 |
Example 1 |
good |
none |
no change |
0.01 |
3770 |
Example 2 |
good |
none |
no change |
0.01 |
3650 |
Example 3 |
good |
none |
no change |
0.01 |
3420 |
Example 4 |
good |
none |
no change |
0.01 |
3370 |
Comparative Example 2 |
good |
none |
no change |
0.01 |
2890 |
Comparative Example 3 |
good |
none |
no change |
0.01 |
3060 |
Comparative Example 4 |
good |
none |
no change |
0.01 |
2960 |
Comparative Example 5 |
good |
none |
no change |
0.01 |
2670 |
Comparative Example 6 |
good |
none |
no change |
0.01 |
2550 |
INDUSTRIAL APPLICABILITY
[0051] In the present invention, the mineral oil component containing sulfur is added to
the synthetic oil component comprising the polyether compound having the specific
properties so that the refrigerating oil contains sulfur derived from the mineral
oil in a specific relative amount. The lubricity can be improved without adverse effects
on compatibility of the polyether compound with natural substance based refrigerants
selected from the group consisting of ammonia, propane, butane and carbon dioxide,
and, in particular, with ammonia-based refrigerants.